Dynamics of electronic motion when the nuclei are clamped is discussed and shown to be always described as a superposition of adiabatic electronic states. These states are stationary when the nuclei are ... [more ▼]

Dynamics of electronic motion when the nuclei are clamped is discussed and shown to be always described as a superposition of adiabatic electronic states. These states are stationary when the nuclei are clamped but their superposition leads to multiply periodic motion where the natural frequencies are the differences in the energies of the adiabatic electronic states. When one or more of the frequencies are low and the atoms are allowed to move, the electronic rearrangement is commensurate with the motion of the nuclei. This is the usual breakdown of the Born-Oppenheimer approximation. But when the electronic frequencies are higher there is an electronic motion before the nuclei move. The motion can be demonstrated through expectation values such as the multipole moments of the charge distribution. Such superposition states will be excited when the laser pulse width in energy exceeds the spacings of the states. For low-lying valence excited or low Rydberg states this requires a femtosecond or shorter laser pulse. Since the carrier frequency has to be comparable to the excitation energy, the required laser pulses must span only a few cycles. [less ▲]

Theoretical transition probabilities are reported for doubly ionized gold (Au III). They have been obtained through the use of two different independent theoretical approaches, i.e. the SUPERSTRUCTURE ... [more ▼]

Theoretical transition probabilities are reported for doubly ionized gold (Au III). They have been obtained through the use of two different independent theoretical approaches, i.e. the SUPERSTRUCTURE code and a HFR model including valence–valence and core–valence configuration interaction in a detailed way. The new scale of A-values is assessed through the comparison of the two sets of results and also through the use of a model similar to the one selected for an isoelectronic ion, i.e. Pt II, for which accurate laser-induced-fluorescence lifetimes have been measured recently. [less ▲]

New experimental lifetimes for two levels in doubly ionized tungsten, W III, have been obtained using the time-resolved laser-induced-fluorescence technique. Theoretical oscillator strengths obtained from ... [more ▼]

New experimental lifetimes for two levels in doubly ionized tungsten, W III, have been obtained using the time-resolved laser-induced-fluorescence technique. Theoretical oscillator strengths obtained from a HFR calculation including the effects of core-polarization are reported for all transitions from levels below E < 70 000 cm−1 and with log g f > −2, thus greatly extending our knowledge of the radiative data in W III. Good agreement is found between the calculated lifetimes and the experimental values from this and previous works. These new results fill a gap in the available data for this ion which is expected to play an important role in fusion reactors. [less ▲]

Radiative lifetimes of 11 odd-parity levels of neutral rhenium (Re I) were measured using time-resolved laser-induced fluorescence techniques. For ten levels, there were no previous results available. The new results have been used to assess the accuracy of calculations with a Hartree-Fock-plus-relativistic-corrections model that takes configuration interaction and core-polarization effects into account and they have allowed the deduction of reliable semi-empirical transition probabilities for 81 Re I lines. [less ▲]

Transition probabilities have been calculated with the pseudorelativistic Hartree-Fock (HFR) approach in which core-polarization effects have been included for Deltan = 0 and Deltan = 1 transitions ... [more ▼]

Transition probabilities have been calculated with the pseudorelativistic Hartree-Fock (HFR) approach in which core-polarization effects have been included for Deltan = 0 and Deltan = 1 transitions connecting the 5s(2)5p(2), 5s(2)5p6p. 5s(2)5p4f and the 5s5p(3). 5s(2)5p5d and 5s(2)5p6s configurations of Xe V. The accuracy of the present set of results is partly assessed through comparisons with the few experimental radiative lifetimes available. The reasons for the discrepancies between theory and experiment are outlined. [less ▲]

An overview is given of methods to study weak and strong nonlinear modes in multispecies plasmas, with a discussion of how they correspond (or not) for phenomena at not too strong amplitudes. Reductive ... [more ▼]

An overview is given of methods to study weak and strong nonlinear modes in multispecies plasmas, with a discussion of how they correspond (or not) for phenomena at not too strong amplitudes. Reductive perturbation analysis leads for weak nonlinear waves to several well known nonlinear evolution equations. In contrast, strong nonlinear phenomena are dealt with by immediately looking for stationary solutions of the model equations. While this works well for electrostatic modes via the Sagdeev pseudopotential technique, large amplitude, parallel propagating solitary electromagnetic waves occur as oscillitons, for which the correct nonlinear evolution equation is still lacking. Electromagnetic modes in (relativistic) electron-positron plasmas are an exception, in that they give pure solitons, both at large and smaller nonlinear amplitudes. The behaviour of the wave magnetic field is expressed through an energy integral that involves the Mach number of the structure, thus yielding the limits on the allowable Mach numbers and soliton amplitudes. [less ▲]

Recent advances regarding radiative parameters determination for rare- earth atoms and ions are briefly discussed. In particular the difficulties associated with both the theoretical and the experimental ... [more ▼]

Recent advances regarding radiative parameters determination for rare- earth atoms and ions are briefly discussed. In particular the difficulties associated with both the theoretical and the experimental investigations of the elements or ions of this group are emphasized. The present status of the DREAM database is also briefly described. [less ▲]

We present an overview of the recent developments concerning the spectroscopic properties of lanthanide atoms and ions (Z = 57-71). This review is focussed on the advances made during the past twenty ... [more ▼]

We present an overview of the recent developments concerning the spectroscopic properties of lanthanide atoms and ions (Z = 57-71). This review is focussed on the advances made during the past twenty years regarding the analysis of the spectra, the transition probabilities, the radiative lifetimes and also the hyperfine structures and isotope shifts. Theoretical aspects as well as experimental measurements are both covered in this paper including bibliographical references up to the end of 2001. Some astrophysical implications of the new atomic data concerning the chemical composition of the sun are briefly reviewed. Emphasis is also put on the new database D.R.E.A.M. developed on a web site of Mons University in Belgium. [less ▲]

We have recorded hollow-cathode spectra of neutral vanadium by Fourier transform spectroscopy in the near infrared - visible region (9000-17 000 cm-1). 36 transitions showing hyperfine structure have been ... [more ▼]

We have recorded hollow-cathode spectra of neutral vanadium by Fourier transform spectroscopy in the near infrared - visible region (9000-17 000 cm-1). 36 transitions showing hyperfine structure have been analyzed, allowing us to deduce magnetic dipole constants for 27 levels belonging to the 3d44p and 3d34s4p configurations. For 22 of these levels no data were previously available. [less ▲]